1. Technical Field
The present invention relates to a liquid ejection head such as an ink jet recording head which applies pressure variations to a pressure chamber communicating with nozzles to eject liquid in the pressure chamber from the nozzles.
2. Related Art
Liquid ejection heads configured to eject liquid in a pressure chamber from nozzles as liquid droplets by generating pressure variations include, for example, an ink jet recording head (hereinafter referred to simply as “recording head”) used in an image recording apparatus such as ink jet recording apparatuses (hereinafter, referred to simply as “printer”), coloring material ejection heads used for manufacturing color filters used in liquid crystal displays, electrode material ejection heads used for forming electrodes for organic EL (Electro Luminescence) displays and FEDs (surface emission-type display), and biological organic substance ejection heads used for manufacturing biochips.
For example, the recording head described above is configured by attaching a flow channel unit formed with a consecutive liquid flow channel from a reservoir via the pressure chamber to the nozzles or an actuator unit having a pressure generating element which is capable of varying the volume of the pressure chamber to a resin-made head case. The above-described flow channel unit includes a metallic nozzle plate having a plurality of nozzles joined thereto.
Liquid to be ejected from the recording head as described above has a viscosity suitable for ejection such as 4 mPa·s at normal temperatures according to the type of the liquid. The viscosity of the liquid has a correlation with the temperature. Therefore, the liquid increases in viscosity with decrease in temperature, and decreases in viscosity with increase in temperature. Therefore, in order to maintain the viscosity of the liquid to be ejected from the respective nozzles to a viscosity suitable for ejection, a configuration including a heating layer for heating the liquid provided right below the reservoir in the flow channel unit, and a heat-insulating layer provided below the heating layer is proposed (see JP-A-2008-296498).
However, since the heating layer is provided right below the reservoir, the heat added to the liquid in the reservoir is radiated in the liquid flow channel extending to the nozzles, so that the temperature of the liquid might be lowered before being ejected from the nozzles. In other words, a set temperature of the heating layer is diverged from the temperature of the liquid at the nozzles, so that there is a possibility that the viscosity of the liquid cannot be adjusted adequately.